1. Field of the Invention
The present invention relates to a tool, a tool holder, and a machine tool.
2. Description of the Related Art
A machining center is a multiple-function machine tool able to perform various types of machining operations such as facing, drilling, boring, and tapping. The multiple-function machining by a machining center includes machining using so-called attachments having certain mechanisms at the tools themselves. As such attachments, for example, there are known ones which change the orientation of the cutter with respect to the spindle of the machining center, ones which increase the rotational speed of the cutter from the rotational speed of the spindle, etc.
Attachments able to change the orientation of the cutter with respect to the spindle to machine a workpiece require a tilt mechanism for changing the posture of the cutter with respect to the spindle, a gear mechanism for transmitting the rotational force of the spindle to the cutter, and other transmission mechanisms.
If there is a tilt mechanism or transmission mechanism between the spindle and cutter, however, the mechanical error of the tilt mechanism or transmission mechanism easily has an effect on the machining accuracy of the workpiece. Further, if there is a gear mechanism etc. between the spindle and the cutter, vibration or heat easily occurs and easily has an effect on the machining accuracy of the workpiece. Further, if using a gear mechanism or other transmission mechanism, the service life is relatively short. Further, since a tilt mechanism or transmission mechanism is built into the limited space of an attachment, the structure easily becomes complicated and the manufacturing cost becomes higher.
An object of the invention is to provide a long service life, low cost tool attachable to a spindle and tool holder enabling a change of posture of the tool with respect to the spindle, giving a high machining accuracy of a workpiece, and generating little vibration or heat.
Another object of the present invention is to provide a machine tool provided with such a tool and tool holder.
According to a first aspect of the invention, there is provided a tool to be attached to a spindle of a machine tool, having a working tool for machining a workpiece, a motor having an output shaft to which the working tool is connected and rotating the working tool, a first holder for holding the working tool and the motor, a mount attached to the spindle, a generator to which rotational force is transmitted from the spindle through the mount and generating electric power for driving the motor, a second holder for holding the mount rotatably, holding the generator, and engaged with a nonrotating portion of the machine tool, and a posture adjustment mechanism connecting the first holder and the second holder in a manner able to change the posture of the working tool with respect to the spindle.
According to a second aspect of the invention, there is provided a tool holder for rotatably holding a working tool for processing a workpiece and attached to a spindle of a machine tool body, having a motor for rotating the working tool, a first holder for rotatably holding the working tool and holding the motor, a mount attached to the spindle, a generator to which rotational force is transmitted from the spindle through the mount and generating electric power for driving the motor, a second holder for holding the mount rotatably, holding the generator, and engaged with a nonrotating portion of the machine tool, and a posture adjustment mechanism connecting the first holder and the second holder in a manner able to change the posture of the working tool with respect to the spindle.
According to a third aspect of the invention, there is provided a machine tool having a machine tool body comprising a spindle, a drive means for driving the spindle, and at least one control axis for changing a relative position between the spindle and a workpiece; a control unit for controlling the drive of the drive means and control axis in response to a machining program; and a tool attached to the spindle of the machine tool body, wherein the tool is provided with a working tool for processing a workpiece, a motor having an output shaft to which the working tool is connected and rotating the working tool, a first holder for holding the working tool and the motor, a mount attached to the spindle, a generator to which rotational force is transmitted from the spindle through the mount and generating electric power for driving the motor, a second holder for holding the mount rotatably, holding the generator, and engaged with a nonrotating portion of the machine tool, and a posture adjustment mechanism connecting the first holder and the second holder in a manner able to change the posture of the working tool with respect to the spindle.
In the present invention, when the spindle rotates, the generator generates power. The electric power generated by the generator is supplied to the motor. The motor then drives the working tool. The rotational speed of the tool with respect to the rotational speed of the spindle changes in response to the properties of the generator and motor.
Further, in the present invention, it is possible to change the posture of the working tool with respect to the spindle. That is, it is possible to handle various machining operations since the posture of the working tool with respect to a workpiece can be changed. Further, when changing the posture of the working tool, the motor also changes in posture, so there is no need for a transmission mechanism for transmitting rotational power to the working tool.